A new naphthalimide-Pd(II) complex as a light-up fluorescent chemosensor for selective detection of carbon monoxide in aqueous medium

•A fluorescent light-up probe, MENap-Pd, detect CO in aqueous buffer medium.•The fluorescence response is highly selective towards relevant reactive species present in biological system.•This detection was highly sensitive towards CO with a LOD of 1.4 μM.•The probe prompted a more than 9-fold ‘turn-on’ fluorescence response to CO.•The detection mechanism follows the demetallation reaction.